Most nurses are women, but in the higher ranks of the medical profession women are in a ________.

A．scarcity

B．minority

C．minimum

D．shortage

心脏壁自内向外可分为（）。

A、心内膜、心肌膜、心瓣膜

B、内膜、中膜、外膜

C、内皮、内皮下层、心内膜下层

D、粘膜、粘膜下层、外膜

E、心内膜、心肌膜、心外膜